The present invention relates to a resonont or pulsating combustion heating apparatus. More particularly, the present invention relates to a pulsation heating apparatus in which the exhaust gas is low in noxious components, particularly carbon monoxide (CO) and nitrogen oxides (NO.sub.x).
These types of pulsation heating units are known. (Refer to ATZ Automobiltechnische Zeitschrift, vo. 66, issue 2 (February 1964), pp. 31-37). They function on the following principle: By way of the suction pipe and the fuel inlet the fuel/air mixture entering the combustion chamber explodes, i.e., combusts explosively in the combustion chamber. The exhaust gas mixture takes place in the pulsation tube at approximately 100 to 130 hz., determined primarily by its length. During the negative half-cycle of the pressure fluctuation (pulsation) fuel/air mixture is sucked into the combustion chamber; during the positive half-cycle it is ignited. A stable pulsing combustion exists. The resulting heat is removed from the pulsation tube, e.g., by means heating cold air currents or heating water.
The regulation of the existing fuel/air mixture for the combustion in general is such that the air coefficient is somewhat less than 1. The air coefficient is the air/fuel ratio. It is equal to 1 in a stoichiometric combustion. In order to easily attain a steady drive even in a cold apparatus and/or at low outside temperatures, the combustion is relatively "rich", i.e., a fixed excess of fuel is used. However, the "richer" the combustion, the higher the concentration of carbon monoxide (CO) and unoxidized (unburned) hydrocarbons (HC) in the exhaust gas. In order to avoid these, a "lean" combustion would then be desired, i.e., using an air coefficient greater than 1 (in other words, using excess air), thereby resulting in scarcely any difficulty at low temperatures and/or on starting. Lean combustion as well has undesirable consequences, in that the nitrogen oxide (NO.sub.x) concentration in the exhaust gas increases. However, even if one somehow overcomes the problems of "lean" combustion at low temperatures and/or on starting and thereby lowers the CO concentration in the exhaust gas, then the lean combustion would lead to an undesirable elevation of NO.sub.x in the exhaust gas.